Bearing material for dry operation of the sintered bronze type

ABSTRACT

A bearing material for dry operation of the sintered bronze type with a solid lubricant additive, particularly graphite, in a proportion amounting to 12 to 20%, and with at least one element selected from the group consisting of Titanium and a metal of Groups VI, VII and VIII of the Periodic System, present in a proportion of about 4 to 15% for increasing stability, the balance of the material being copper or a known bronze other than binary lead bronze.

United States Patent [191 Mertl BEARING MATERIAL FOR DRY OPERATION OFTHE SINTERED BRONZE TYPE [75] Inventor: Klaus Mertl, Reinbek, Germany[73] Assignee: Jurid Werke GmbH, Glinde near Hamburg, Germany 22 Filed:May 25, 1971 21 App1.No.: 155,675

[30] Foreign Application Priority Data June 6, 1970 Germany 2027902 52U.S.Cl. ..29/1s2.s,252/12 511 lnt.Cl. ...B22f 1/00,c10m 5/28 [58] Fieldof Search .v 29/1825; 252/12 [56] References Cited UNITED STATES PATENTS3,461 ,069 8/1969 Waldhuter 252/12 Mar. 5, 1974 2,983,034 5/1961 Humeniket a1. 24/1825 1,479,859 1/1924 Koehler 11 252/12 FOREIGN PATENTS ORAPPLICATIONS 456,467 5/1949 Canada 29/1825 Primary ExaminerCarl D.Quarforth Assistant ExaminerR. E. Schafer Attorney, Agent, or Firm-Young& Thompson [5 7 ABSTRACT 2 Claims, N0 Drawings BEARING MATERIAL FOR DRYOPERATION OF THE SINTERED BRONZE TYPE SUMMARY OF THE INVENTION Theinvention relates to a bearing material for dry operation, which isbased upon sintered bronze, with an additive for increasing thestability and a solid lubricant additive, particularly graphite.

The choice of the optimum hearing or anti-friction material isparticularly important for many technical products, since in themajority of cases faults which occur in bearings can lead to a suddenbreakdown in the apparatus. This also applies to bearings which are onlylubricated once during installation and wherein additional lubricationis not possible, for example in the food industry or with apparatuswhich is exposed to high temperatures at which known lubricants can nolonger be used. Even extreme high-speed equipment, for example grindingspindles, gas centrifuges etc., do not allow lubrication by means ofoils or grease.

In certain cases, so-called gas suspensions or floating bearings areused, which require bearing materials for dry operation with goodemergency running properties, so that seizure is avoided. Very highdemands are thus imposed on dry-running bearing materials, for duringacceleration and braking direct contact between the materials of thebearing and the shaft cannot be avoided, because the supporting gas filmis only formed at a minimum number of revolutions per unit time,dependent upon the method of construction. Wear and friction of thebearing material must therefore be very low, whilst its strength must beas high as possible.

The best of the previously known sintered bronze anti-friction materialsfor dry operation are the lead bronzes. These have satisfactory frictionvalues, but their strength is not sufficient for all purposes. Thus forexample, the stability of a known sintered lead bronze, consisting byweight of 80% Cu, 8% Pb and 12% C, with a Brinell Hardness (HB 2.5/2.5)of 23 kp/mm is quite inadequate,

The invention is concerned with the problem of removing the previousdisadvantages and of providing an anti-friction material for dryoperation of the sinteredbronze type, which in addition to good wear andsatisfactory friction values also has a satisfactory strength orstability.

This problem is solved by means of a bearing material for dry operationof the type initially described, of the sintered bronze type, with anadditive for increasing stability and with a solid lubricant additive,particularly graphite, wherein according to the invention titaniumand/or metal of Groups VI, VII and VIII of the Periodic System, in aproportion of about 4 to 15% b.w., is used as the first additive, andthe proportion of solid lubricant present amounts to about 12 to 20%b.w., the balance of the material being copper or a known bronze otherthan binary lead bronze.

In general, it is a problem to incorporate in the antifricti'on materialthe amount of lubricant necessary for achieving the desired low frictionvalues, without impairing the resistance. Indeed, it is known that toincrease the stability metals known in steel for the same purpose can beused with the bronzes, e.g., Co, Mo, Mn, Ni. However, in comparison withthe known tin or lead bronzes, higher sintering temperatures arenecessary to obtain a solution of these metals in copper. There is thenthe danger that. with a graphite proportion of 12% b.w. and more, thestructure could then be so impaired that the stability behaviour of suchsystems becomes uncontrollable. it has surprisingly been found thatsintered bronzes with these higher melting additives give mainlysatisfactory results even with a high graphite proportion. With theanti-friction material according to the invention with a weightcomposition of Cu, 5% Co, l5% C, friction speeds of 210 m/sec, thehighest value which the testing apparatus, a gassupported rotator,allows, were easily reached. As opposed to this with the previouslyknown sintered bronze bearing materials, at the most about 170 m/seccould be achieved. The bearing materials according to the invention,with a density of 6 g/cm, had a Brinell hardness value (HB 25/25) of 35kp/mm as opposed to 23 kp/mm with a known lead bronze dry material.

As opposed to the known materials of comparable kind, wherein a highresistance with a low friction value can possibly be achieved by hotpressing, the material according to the invention can be prepared by acomparatively simple common cold pressing method. In addition to theimproved properties of use of the friction materials according to theinvention, there are the additional advantages of a noticeable reductionin weihgt and a simplified and thus weight less expensive possibility ofmanufacture.

The preferred metals used as the additive for increas ing the stabilityin the bearing materials according to the invention are preferably usedin the following particle sizes:

Copper 10 500 um, preferably 5 80 pm;

Manganese 3 200 um, preferably 15 55 um;

Nickel 3 200 um, preferably 15 55 um;

Cobalt 3 200 um, preferably 15 55 am;

Titanium 3 200 am, preferably 15 55 am;

Iron 5 300 ,um, preferably 15 55 am;

Graphite l 1,000 ,u.m, preferably 5 am.

The general nature of the invention having been set forth, the followingexample is presented to illustrate but not to limit the preferred meansfor carrying out the invention.

EXAMPLE Bearing materials according to the invention were produced fromthe above compositions as follows: The constituents were cold pressed inpowder form ofa predetermined particle size in the above ranges at apressure in the range from 2 to 4 Mp/cm they were then sintered at 600to 800C. They were subsequently r epressed at a pressure of 2 to 4 Mp/cmand finally sintered at a temperature of about 70% of the melting pointof the main components, thus in the range of about 900 to l,l0OC. Aftersintering, they were finally pressed (calibrated) up to a residualporous volume of less than 10% with a pressing pressure in the rangefrom 2 to 4 Mp/cm The finished component was then available. This had inall cases a lower weight than the known sintered lead bronzeanti-friction material and a satisfactory friction value with a highresistance, whereas with the known sintered bronze friction materials, asatisfactory friction value was only present with an unsatisfactoryresistance.

Compositions of the bearing materials according to the invention:

weight percent I. 12-20 4-15 Co 4-15 Fe Weight percent Weight percentBalance Cu Balance Cu 3, l2-20 C 4 l 2-20 4- l 5 Ni 4-15 Mn Balance CuBalance Cu 5. l22() C 6 12-20 C 4 l 5 Ti 3-8 Co Balance Cu 1-7 FeBalance Cu 7 12-20 C 8 l2-2t) C 3-8 Co 3-8 Co l-7 Ni l-7 Mn Balan e CuBalance Cu 9, l22() C ll). l2-20 C 38 Co 3-8 Co l-7 Ti l4 Fe Balance Cul-4 Ni Balance Cu I l l2-2U C l2. l2-2t) C 'X-X Co 3-3 Cu l-7 W l-7 MuBalance Cu Balance (u The proportion of copper in these compositions canalso be replaced by known bronzes, such as Cu SnAl,

CuAl. CuSnP. CuSnZn, CuSnPb.

I claim:

ll. A sintered bearing material for dry operation of the sintered bronzetype containing a solid lubricant additive and consisting essentially ofl2 20% by weight graphite, 4 15% by weight otat least one mem berselected from the group consisting of Co. Ni, Fe, Mn, Ti, Mo and W,balance essentially a known alloy composition selected from the groupconsisting of copper, CuSnAl, CuAl, CuSnP, CuSnZn and CuSnPb.

2. A sintered bearing material for dry operation of the sintered bronzetype containing a solid lubricant additive and consisting essentially ofabout by weight copper (particle size 5 80 ,um), about 5% by weightcobalt (particle size 15 55 ,um), and about 15% by weight graphite(particle size 5 um).

2. A sintered bearing material for dry operation of the sintered bronzetype containing a solid lubricant additive and consisting essentially ofabout 80% by weight copper (particle size 5 - 80 Mu m), about 5% byweight cobalt (particle size 15 - 55 Mu m), and about 15% by weightgraphite (particle size 5 - 100 Mu m).